Synthesis, crystal structure, and in vitro antitumor activities of copper(II) complexes containing tetradentate pyridine-based ligands

Abstract

Several new Cu(II) complexes of Schiff bases obtained by condensation of 2-[N-(α-picolyl)-amino]-benzophenone with different chiral amino acids were synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structure of one of the complexes was determined using single crystal X-ray diffraction. The ligands were coordinated to the metal atom in a tetradentate manner with ONNN donor sets using the carboxyl oxygen, azomethine nitrogen, CON−, and pyridine nitrogen. The cytotoxicities of the complexes were evaluated against human cancer cells. The substituents on the aromatic rings strongly influenced the cytotoxicities of the complexes. The complex with bromine substituents on the pyridine rings showed the highest cytotoxicity. The antitumor activities against tumor cell lines were assayed in vitro, and the complexes were found to be highly effective, with six of the nine complexes having inhibition ratios better than that of 5-Fluorouracil. This behavior is indicative of a high ability to circumvent the cellular drug resistance mechanisms.